Update for Civil Surgeons: Option of Using Interferon Gamma Release Assay in Place of Tuberculin Skin Test

October 30, 2009

The Tuberculosis Component of the Technical Instructions for Medical Examination of Aliens in the United States (May 2008) have heretofore required administration of a tuberculin skin test (TST) to all applicants 2 years of age and older, and to applicants less than 2 years of age when there has been known contact with a tuberculosis (TB) case or other reason to suspect TB. The TST provides a measure of cell-mediated immunity. Its result determines whether a chest radiograph is needed to evaluate for pulmonary TB.

To fulfill the requirement of testing for cell-mediated immunity to TB, civil surgeons may now administer an interferon gamma release assay (IGRA) or a TST. Interferon gamma release assays are blood tests that measure a component of cell-mediated immune reactivity to Mycobacterium tuberculosis in fresh whole blood. CDC allows the use of QuantiFERON-TB Gold®, QuantiFERON®-TB Gold In Tube (QFT-G IT), and T-SPOT®. The civil surgeon should administer only one type of test for cell-mediated immunity (TST, QuantiFERON-TB Gold®, QuantiFERON®-TB Gold In Tube [QFT-G IT], or T-SPOT®) to each applicant.

Civil surgeons performing an IGRA should follow the manufacturer’s written instructions for performing the examination and interpreting the test result.

An indeterminate or borderline/equivocal result on IGRA assay should be treated as a negative result.

Exceptions to required testing for cell-mediated immunity are—

• Applicants providing written documentation (with a health-care provider’s signature) of a TST reaction of 5 mm or greater of induration. For TST, the written documentation must include date of the test, millimeters of induration, type of PPD used, and the testing health-care provider’s name, signature, and office information. A verbal history from the applicant of a positive TST reaction is not acceptable.
• Applicants who have a history of a severe reaction with blistering to a prior TST
• Applicants providing written documentation (with a health-care provider’s signature) of a prior positive IGRA. If more than one IGRA has previously been performed, the most recent result should be used. The written documentation must include date of the test, type of IGRA performed, test results including units of measurement, and the testing health-care provider’s name, signature, and office information. A verbal history from the applicant of a positive IGRA result is not acceptable.

If one of the tests has previously been positive as described above, a chest radiograph is required. In this circumstance, the civil surgeon should not perform another type of cell-mediated immunity test to attempt to achieve a negative result.

Many applicants may have previously received Bacille Calmette-Guérin (BCG) vaccination. Prior receipt of BCG does not change the cell-mediated immunity testing requirement or the required actions based on those results.

If the test for cell-mediated immunity is negative but the applicant has signs or symptoms of TB or is immunosuppressed, a chest radiograph is required.

CDC recommends that civil surgeons refer applicants with a positive TST or IGRA result and a negative chest radiograph, to the health department TB Control Program for evaluation for treatment of latent M. tuberculosis infection (LTBI).

U.S. Citizenship and Immigration Services (USCIS) has released a new I-693 form to incorporate the cell-mediated immunity testing update and other changes. It is available on the USCIS website (http://www.uscis.gov/portal/site/uscis). It replaces the I-693 form currently found in Appendix D of the 2008 Tuberculosis Component of Technical Instructions for the Medical Examination of Aliens in the United States.